Screw-operated electrical connector



Feb 5, 1957 J. c. GAMBALE SCREW-OPERATED ELECTRICAL CONNECTOR Filed Dec. 8, 1954 WITNESSESI 547 2/ INVENTOR John C.Gombole. BY

29 I5 ATTORNEY nited States Patent SCREW-OPERATED ELECTRICAL CONNECTOR John C. Gambale, East Orange, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 8, 1954, Serial No. 473,815

3 Claims. (Cl. 339-272) My invention relates, generally, to terminal connectors and, more particularly, to connectors of the type generally known as solderless connectors in which contact between conductors is maintained by pressure and not by utilizing solder.

The termination of aluminum conductors in solderless connectors presents somewhat different problems from the termination of copper conductors. A film of aluminum oxide forms rapidly on the surface of aluminum when it is exposed to oxygen. The film is a poor conductor of electricity but is brittle and can be broken easily.

Also, aluminum is relatively soft, and it has a tendency to cold flow under pressure. This tendency is accentuated when an aluminum conductor is clamped in a connector composed of a metal having a coefficient of expansion which is different from that of aluminum.

An object of my invention, generally stated, is to provide a terminal connector which shall be simple and eflicient in operation and which may be economically manufactured and installed.

A more specific object of my invention is to provide a solderless connector having a relatively low unit pressure on the conductor held in the connector.

Another object of my invention is to compensate for the difference in the coefiicients of expansion of a conductor composed of one metal and a connector composed of another metal.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

in accordance with one embodiment of my invention, a generally U-shaped body member and an L-shaped clamping member are hinged together to form substantially a closed rectangle for holding a conductor. The end edges of a resilient pressure plate, which, preferably, is curved longitudinally of the conductor, are pressed into the conductor by turning a screw which carries the pressure plate and is threaded in one leg of the L-shaped clamping member. Thus, the conductor is held firmly in the connector without applying excessive pressure on the conductor, and the resiliency of the pressure plate compensates for the difference in the coefficients of expansion of the conductor material and the terminal connector material.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure l is an exploded view of a terminal connector embodying the principal features of the invention;

Fig. 2 is a view in end elevation of the connector; and

Pi g. 3 is a view in section taken along the line Ill-III in Fig. 2.

Referring to the drawing, and particularly to Fig. 1, the terminal connector shown therein comprises a body member 10, a clamping member 11, a screw 13, which is threaded into the clamping member 11, and a pressure plate 14, which is rotatably mounted on the screw 13. As shown, the body member is, generally, of a U-shape having a base and legs 16 and 17. It will be noted that the legs are of unequal length, the leg 16 being longer than the leg 17. A rectangular opening 18 is provided adjacent the end of the leg 16. A tongue 19, which is reduced in width, is bent outwardly substantially at a right angle to the leg 17.

The clamping member 11 is, generally, of an L-shape. A generally rectangular opening 21 is provided in a shorter leg 22 and extends into the bend between the shorter leg 22 and a longer leg 23 of the L-shaped member 11. A threaded opening 24 is'provided in the longer leg 23 for the screw 13. A tongue 25 of a reduced width is provided at the end of the longer leg 23. The members 10 and 11 may be composed of brass, or a similar material having suflicient mechanical strength.

The lower end of the screw 13 is reduced in diameter for receiving the pressure plate 14. After the plate is placed on the reduced end of the screw, the end may be upset or riveted at 26 to retain the pressure plate on the screw. However, the screw 13 must be free to rotate in the pressure plate.

The pressure plate 14 is preferably composed of a resilient material as, for example, beryllium copper or stainless steel. As shown most clearly in Figs. 1 and 3, the plate 14 is generally rectangular in shape and is curved longitudinally. The ends of the plate are cut off square, thereby providing relatively sharp end edges.

As shown most clearly in Fig. 2, the terminal connector is assembled by placing the tongue 19 in the opening 21 in the clamping plate 11. The opening 21 is of sufficient width to permit conductors of dififerent sizes to be held in the connector. Thus, as shown, a relatively large conductor 27 is held in the connector. One side of the opening 21 and the tongue 19 function as a pivot or hingefor the clamping member 23 to permit the tongue 25 on the clamping member to be inserted in the opening 18 in the body member after the conductor 27 is placed in the body member. Thus, the clamping member may be swung out of the way or entirely removed from the body member to permit the conductor 27 to be placed in the body member by laying it between the two legs of the body member rather than inserting it endwise into the body member. This is an advantage when it is necessary to install large conductors in a relatively small space, as the conductor may be installed without it being necessary to bend the end of the conductor.

As shown, the base 15 of the body member may be attached to a terminal conductor 28 by means of a screw 29. The conductor 28 may be connected to the terminal of a circuit breaker, or a meter, or any other electrical device. The terminal conductor may be composed of brass or copper or other material having a high electrical conductivity.

As shown most clearly in Fig. 3, end edges 31 and 32 of the longitudinally curved pressure plate 14 are pressed into the conductor 27 when the screw 13 is tightened. Thus, the conductor 27 is held firmly in the connector, and longitudinal movement of the conductor in either direction is prevented without it being necessary to apply extreme pressure on the conductor. Therefore, the tendency of an aluminum conductor to cold flow is reduced since it is not necessary to apply an extreme pressure on the conductor.

Also, the resiliency of the pressure plate 14 compensates for the difference in the coeflicients of expansion of brass and aluminum, thereby preventing the pressure on the conductor from being increased by the difference in expansion of the dissimilar metals. Accordingly, the tendency of the conductor to become loosened in the connector by expansion and contraction is reduced.

As previously explained, the pressure plate may be made of stainless steel, heat treated to give it the desired spring characteristics. A plate having a deflection of approxir mately 0.009 of an inch under atightening torgueof 75 inch-pounds has proven satisfactory. This gives the plate 0.009 of an inch of spring follow-up when the screw in the terminal is tightened.to;75 inchrpounds with a=bearing pressure onithe cable 051,800 p. s. i.

From the foregoing description, it is apparentrthat I have provided a terminal connector which, is particularly suitable for holding conductors composed of aluminum, or other relatively soft material, and which will accommodate conductors of different sizes. The present connector is relatively simple in structure and may be manufactured and sold at a relatively low cost.

- Since numerous changes may be made in the abovedescribed construction, and difierent embodiments ofthe invention may be made without departing from the spirit and scopethereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

' 1. In a connector for holding an electrical conductor, in combination, a body member and a clamping member removably joined together to hold the conductor, a screw threaded in the clamping member, an elongated resilient pressure plate rotatably carried. by the screw, said plate having relatively sharp end edges extending substantially at right angles to the side edges of the plate, said plate being curved longitudinally of the conductor to cause said end edges of the plate to be pressed into the conductor when the screw is tightened, and said plate being composed of a harder material than said conductor and having a higher resilience than said conductor.

2. In a connector for holding an electrical conductor, in combination, a generally U-shaped body member, a

enerally Lrshaped. l mp mem n o e eg hinged on one leg of the body member, a screw threaded in the other leg of the clamping member, an elongated resilient pressure plate rotatably attached to the screw substantially midway between the ends of the plate, said plate having relatively sharp end edges extending substantially at right angles to the side edges of the plate, and said platejbeing curvedlongitudinally of the conductor to cause said endredges of the plate to be pressed into the conductor when the screw is tightened;

3. In a connector for holding an electrical conductor, in combination, a body member and a clamping member removably joined together to hold the conductor, a screw threaded in the clamping member, an elongated resilient pressure plate rotata'bly attached to the screw substantially midway between the ends of the plate, said plate having relatively sharp end edges extending substantially at right angles to the side edges of the plate, and said plate being curved longitudinally of the conductor to cause said end edges of the plate-to be pressed into lhQCOIlClHClOI when the screw is tightened.

References Cited in the file of this patent UNITED STATES PATENTS 2,009,289 Caird July 23, 1935 2,117,112 Buchanan May 10, 1938 2,145,556 Rypinski Jan. 31, 1939 2,265,911 Landmeier Dec. 9, 1941 2,453,432 Hakathorn Nov. 9, 1948 2,546,395 Hubbard Mar. 27, 1951 2,574,776 Clapp Nov. 13, 1951 FOREIGN PATENTS 344,112 Great Britain Mar. 5, 1931 

